They said the suspect in the shootings is 44-year-old Erbie Bowser, who was dating Smith. Zina Bowser was Bowser's estranged wife, they said.

When asked about a possible motive, DeSoto police spokesman Nick Bristow said that authorities believe "it just to be an isolated domestic issue."

The Dallas Mavericks said Bowser used to be a member of the NBA team's Mavs ManiAACs, an all-male hip-hop dance troupe that entertains fans at games. He left the squad in 2009, Mavericks spokesman Scott Tomlin said.

Bowser was a special education teacher for Mesquite Independent School District east of Dallas from December 2001 through March 2010, last teaching at Berry Middle School, district spokeswoman Laura Jobe said. He resigned and "left us on good terms," she said.

Authorities learned of the Dallas shootings at 10:30 p.m., when relatives found the carnage there and called 911, police said.

Beforehand, one of the victims had talked to her mother on the phone. Something about the conversation concerned the mother, so after calling back and getting no response, she drove with some family members to the Dallas home, where they saw the four who had been shot, Dallas police Maj. Jeff Cotner said.

Toya Smith and her 17-year-old daughter were dead inside the house. Injured were the woman's 14-year-old son and a 17-year-old girl who was a family friend, Cotner said.

The 14-year-old was in critical condition Thursday.

Dallas police had reason to suspect the gunman might have a DeSoto connection, and called DeSoto police, Cotner said.

Minutes later -- at 10:45 p.m., while police were traveling to check the DeSoto home -- a child called 911 to report the shooting there, DeSoto police spokeswoman Melissa Franks said.

The gunman had used "some sort of explosive device," and then shot at the people inside, Franks said.

Zina Bowser and Neima Williams were killed there, and two boys -- ages 11 and 13 -- were injured, she said. Both were in critical condition Thursday.

Police arrested the suspect there without incident, she said.

Dallas and DeSoto investigators are working together on the case. The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives is investigating the nature of the explosive device, Franks said.